Method of obtaining arsenious oxide



Patented Mar. 3, 1925. V

UNITED STATES 1,528,004 PATENT, OFFICE. I

HARRY P. BASSETT, OF CYNT'I-IIANA, KENTUCKY, AND SAMUEL S. SADTLER, OF SPRINGFIELD TOWNSHIP, MONTGOMERY COUNTY, PENNSYLVANIA.

METHOD or o-sramme ARSENIOUS OXIDE.

No Drawing,

To all whom it may concern Be it known that we, HARRY P. BASSETT and SAMUEL S. SADTLER, citizens of the- United States, residing at Cynthiana, in the county of Harrison and State of Kentucky, and Springfield Township, in the county of Montgomery and State of Pennsylvania,'respectively, have invented certain new'and useful Improvements in Methods of Obtaining Arsenious Oxide, of which'the following is a specification. 7

Our invention relates to an economical method of obtaining arsenious oxide from naturally occurring ores of arsenic, such as speisses, mispickels, realgar,.orpiment, in which arsenic exists essentially as sulphide or compound sulphide with other metals containing arseni An important object of the invention is the provision of methods of treating such ores which are more economical than any now practiced in the. production or recovery of arsenic as a valuable product or by-prod-' not. Our process of separating arsenic as it occurs as speisses, mispickels, and in association with sulphur and heavy metals broadly, consists in controlled heating of finely powdered ore at relatively lowtemperatures and with slight and regulated admission of air. Under such circumstances the arsenic is evolved and leaves the sulphur combined with iron, nickel, cobalt, or other heavy metals, or metals with which the arsenic ocours.

We are aware of attempts to remove arsenic as disclosed by Ernest V. lVestcott, in United States Patent No. 1306,5597, granted February 14, 1922, in which chlorine is used to combine with the arsenic and render it volatile. This is, however, distinctly different from the present invention. The British patent to Oxland and Hockings, N 0. 2,950, of 1868, relates to revolving c'alciners and refers to the fact that arsenic comes off first but it shows no means for controlling the heat and air admission. They completely oxidize the ore. This is in fact whathas been and is now the practice at smelters. They drive off both arsenic and sulphur. Oxland and Hockings', furthermore, did not recognize one of the features of our invention, as applied especially to speisses, etc., that is necessary for low temperature and high yield results: namely, the presence of at least combining equivalents Application filerl- February 25, 1924. Serial No. 695,100.

(with reference to the sulphur) of metals forming stable sulphides at temperatures prevailing in this low temperature heating and distillation.

' In practicing the invention, we use muffle furnaces, preferably'rotary, taking the necessary'prec autions toavoid' a flame that is too strongly oxldlzing. The temperatures we have found necessary are so low, however, that we prefer touse the former method, namely, muffle heating.

In a typical embodiment of the invention, the ore is finely ground, say to 100 mesh, and there may be added c'oke'or some other form of carbon .or even a little carbon alone, to prevent any burning of the ore. The addition of carbon, however, should not be found necessary with sulphides, if the heat is carefully controlled. In our preferred form of apparatus, we use a substantially closed iron tube without fire brick, which is slowly revolved at a suitable inclination in a flue from a relatively small fire box. ore or ore mixture passes down through the tube to an ore trap at the lower end. The arsenic fumes with varying amounts of arsenious oxide (depending upon the admis sion of air) pass upwards to oxidizing and condensing chambers and filters. The temperature in the tube is usually distinctly below red heat. We havensed temperatures between 200 C. and 400 (3., but especially avoid any temperatures as high as even d'ull redness unless there is sufficient carbonto protect the ore, when higher temperatures may be used. The arsenic is recovered as arsenious oxide (white arsenic). Enough air may be admitted into the furnace to just burn the arsenic evolved from the ore, but we prefer to admit air above the ore and near the flue entrance so that it does not actuallyv come in contact with the ore except in an attenuated state.

An alternative to this procedure is to admit no air to the mufile and to oxidize the evolved arsenic in the receiving chamber, but we prefer to oxidize the arsenic in the upper part of the muffle. If a small amount of carbon is admixed with the ore, there is less danger of burning the ores.

The main reaction involved seems to be:

)Vhile we have described in detail the preferred practice of our process, it is to be The powdered understood that the details of procedure, and proportion of ingredients may be widely varied, and that known chemical equivalents may be employed in place of the materials mentioned, without departing from the spirit of the invention or the scope of the subjoined claims.

We claim:

1. The method of obtaining arsenious oxide from ores containing arsenic associated with sulfur and heavy metals which comprises heating the ore to a regulated temperature in the presence of a limited amount of air insufficient to oxidize the sulfur present.

2. The method 1 of obtaining arsenious oxide from ores containing arsenic associated with sulfur and heavy metals, which comprises heating the ore to a temperature below 400 C. in the presence of sufiicient amount of air to oxidize the evolved arsenic.

3. The method of obtaining arsenious oxide from ores containing arsenic associated with sulfur and heavy metals which comprises heating the ore to a temperature between 200 C. and @00 C. in the presence of suiiicient air to oxidize the evolved arsenic.

4:. The method of obta ining arsenious oxide from ores containing arsenic associated with sulfur and heavy metals which comprises reducing the ore to a powder, adding carbon thereto, and heating to a temperature below 400 C. in the presence of a limited amount of air insuflicient to oxidize the sulfur present.

5. The process of obtaining arsemous oxide from ores consisting of sulphides of arsenic and other metals which comprises heating the ore at a low temperature such as will release the arsenic and form sulphides of the other metals, and admitting suflicient air to oxidize the evolved arsenic to the tri-oxide.

In testimony whereof, we aiiix our signatures in presence of a witness.

HARRY P... BASSETT.

SAMUEL S. SADTLEB. WVitness:

A. M. Scroxns. 

